The present invention relates to a process for preparing 4-hydroxyphenylacetic acid.
4-Hydroxyphenylacetic acid is useful as an intermediate of pharmaceuticals and agricultural chemicals.
As an industrially advantageous process for the preparation of 4-hydroxyphenylacetic acid, there is proposed a process by catalytic reduction of 4-hydroxymandelic acid, and one of the most preferable embodiment of the process is the catalytic reduction of 4-hydroxymandelic acid, especially the sodium salt thereof with palladium catalyst in water medium in the presence of a large amount of hydrochloric acid. However, such a process involves problems that (1) the yield of 4-hydroxyphenylacetic acid is at most 85% by mole to 4-hydroxymandelic acid, and that (2) because of the use of a large amount of hydrochloric acid, the desired product is contaminated with a large amount of a neutralized salt and the purification is troublesome, and an apparatus is in danger of corrosion. For these reasons, further improvements are desired in the operation and the quality of the product in the industrial production.
Accordingly, it is an object of the present invention to provide an improved process for preparing 4-hydroxyphenylacetic acid.
A further object of the invention is to provide a process for preparing 4-hydroxyphenylacetic acid of high quality in high yields.
These and other objects of the invention will become apparent from the description hereinafter.